The present invention provides devices and methods for the endoluminal placement of prostheses, particularly within the vascular system for the treatment of cardiovascular disease, such as vascular stenoses, dissections, aneurysms, and the like. The apparatus and methods, however, are also useful for placement in other body lumens, such as the ureter, urethra, biliary tract, gastrointestinal tract and the like, for the treatment of other conditions which may benefit from the introduction of a reinforcing or protective structure within the body lumen. The prostheses will be placed endoluminally. As used herein, xe2x80x9cendoluminallyxe2x80x9d will mean placement by percutaneous or cutdown procedures, wherein the prosthesis is transluminally advanced through the body lumen from a remote location to a target site in the lumen. In vascular procedures, the prostheses will typically be introduced xe2x80x9cendovascularlyxe2x80x9d using a catheter over a guidewire under fluoroscopic guidance. The catheters and guidewires may be introduced through conventional access sites to the vascular system, such as through the femoral artery, or brachial and subclavian arteries, for access to the target site.
An endoluminal prosthesis typically comprises at least one radially expansible, usually cylindrical, body segment. By xe2x80x9cradially expansible,xe2x80x9d it is meant that the body segment can be converted from a small diameter configuration (used for endoluminal placement) to a radially expanded, usually cylindrical, configuration which is achieved when the prosthesis is implanted at the desired target site. The prosthesis may be non-resilient, e.g., malleable, thus requiring the application of an internal force to expand it at the target site. Typically, the expansive force can be provided by a balloon catheter, such as an angioplasty balloon for vascular procedures. Alternatively, the prosthesis can be self-expanding. Such self-expanding structures are provided by a temperature-sensitive superelastic material, such as Nitinol, which naturally assumes a radially expanded condition once an appropriate temperature has been reached. The appropriate temperature can be, for example, a temperature slightly below normal body temperature; if the appropriate temperature is above normal body temperature, some method of heating the structure must be used. Another type of self-expanding structure uses resilient material, such as a stainless steel or superelastic alloy, and forming the body segment so that it possesses its desired, radially-expanded diameter when it is unconstrained, e.g., released from radially constraining forces a sheath. To remain anchored in the body lumen, the prosthesis will remain partially constrained by the lumen. The self-expanding prosthesis can be delivered in its radially constrained configuration, e.g. by placing the prosthesis within a delivery sheath or tube and retracting the sheath at the target site. Such general aspects of construction and delivery modalities are well-known in the art and do not comprise part of the present invention.
The dimensions of a typical endoluminal prosthesis will depend on its intended use. Typically, the prosthesis will have a length in the range from 0.5 cm to 10 cm, usually being from about 0.8 cm to 5 cm, for vascular applications. The small (radially collapsed) diameter of cylindrical prostheses will usually be in the range from about 1 mm to 10 mm, more usually being in the range from 1.5 mm to 6 mm for vascular applications. The expanded diameter will usually be in the range from about 2 mm to 42 mm, preferably being in the range from about 3 mm to 15 mm for vascular applications.
One type of endoluminal prosthesis includes both a stent component and a graft component. These endoluminal prostheses are often called stent grafts. A stent graft is typically introduced using a catheter with both the stent and graft in contracted, reduced-diameter states. Once at the target site, the stent and graft are expanded. After expansion, the catheter is withdrawn from the vessel leaving the stent graft at the target site.
Grafts are used within the body for various reasons, such as to repair damaged or diseased portions of blood vessels such as may be caused by injury, disease, or an aneurysm. It has been found effective to introduce pores into the walls of the graft to provide ingrowth of tissue onto the walls of the graft. With larger diameter grafts, woven graft material is often used. In small diameter vessels, porous fluoropolymers, such as PTFE, have been found useful.
Coil-type stents can be wound about the catheter shaft in torqued compression for deployment. The coil-type stent can be maintained in this torqued compression condition by securing the ends of the coil-type stent in position on a catheter shaft. The ends are released by, for example, pulling on wires once at the target site. See, for example, U.S. Pat. Nos. 5,372,600 and 5,476,505. Alternatively, the endoluminal prosthesis can be maintained in its reduced-diameter condition by a sleeve; the sleeve can be selectively retracted to release the prosthesis. A third approach is the most common.
A balloon is used to expand the prosthesis at the target site. The stent is typically extended past its elastic limit so that it remains in its expanded state after the balloon is deflated. One balloon expandable stent is the PALMAZ-SHATZ stent available from the CORDIS Division of Johnson and Johnson. Stents are also available from Arterial Vascular Engineering of Santa Rosa, California and Guidant Corporation of Indianapolis, Indiana.
The present invention is directed to a catheter assembly including an endoluminal prosthesis, such as a stent, a graft, a stent graft or other endoluminal structure, and a catheter having at least first and second telescoping shafts to which the prosthesis is releasably engaged. The distal end portions of the telescoping shafts include prosthesis portion holders. The prosthesis is capable of assuming a second, expanded diameter state from a first, reduced diameter state and is releasably engagable with the first and second prosthesis portion holders. The catheter assembly is especially useful for placing the endoluminal prosthesis at the intersection of a bifurcation within a blood vessel.
The prosthesis may be a coiled stent graft in which one turn of the prosthesis has a greater pitch than the adjacent turns. This permits substantially unrestricted fluid flow between a first vessel housing the prosthesis and a branching vessel when the prosthesis is properly placed with the at least one turn at the intersection of the first and branching vessels.
When the at least one turn is at an end of the prosthesis the prosthesis can be properly placed using only the first and second telescoping shafts. When the at least one turn is at a central portion of the prostheses, it is preferred that the catheter shaft include a third telescoping and rotatable shaft which can also releasably engage the prosthesis. The prosthesis is typically engaged at each end and at the at least one turn by the prosthesis engaging portions of the shafts.
The prosthesis and/or the catheter shaft may also include remotely viewable marker elements at spaced apart positions. At least one of the marker elements is preferably located at the at least one turn, so to aid proper placement of the prosthesis at the intersection of the first and branching vessels. One or more of the marker elements may be configured to indicate orientation as well as axial position.
The ends of the prosthesis are preferably substantially less stiff than the remainder of the prosthesis. This provides several advantages. It tends to cause the ends of the prosthesis to open up first in the center and then at the end areas to reduce abrasion of the vessel walls by the ends. Also, by the ends being less stiff than the remainder of the prosthesis, injury to the vessel walls is less likely. Also, the end portions of the prosthesis may have an inwardly-tapering portion with a blunt tip, again to help prevent tissue trauma.
A further aspect of the invention relates to a method for placing an endoluminal prosthesis within a body. The method includes introducing the distal portion of a catheter assembly at a chosen position within the body. The distal portion includes a coiled stent graft wound about a catheter shaft and capable of assuming a second, expanded-diameter state from a first, reduced-diameter state. The turns of the stent graft have spaces therebetween when in the second state. The pitch of at least one turn is greater than the pitch of adjacent turns. The stent graft is releasably connected to the catheter shaft at first and second positions along the stent graft. The first position is at the at least one turn. The at least one turn is then located at an intersection of a first vessel and a branching vessel. The second position of the stent graft is then released from the catheter to permit at least a portion of the stent graft to expand while maintaining the first position of the stent graft at the intersection. The remainder of the stent graft, including the first portion, is then released permitting the remainder of the stent graft to expand. When the at least one turn is at a central position of the stent graft, the central position is preferably released after ends have been released.
It is preferred that the introducing step be carried out using a catheter shaft including first and second rotatable, telescoping shafts with the first and second positions of the stent graft releasably connected to the first and second telescoping shafts. This permits the telescoping shafts to be longitudinally moved relative to one another to selectively change the length of the stent graft or rotated relative to one another to selectively change the number of turns of the stent graft.
If desired more than one stent graft can be used along the first vessel or along a branching vessel or both. The stent graft may have different diameters when in the second, expanded state to accommodate different diameters within a vessel.